Chapter 46. Logical Decoding

Table of Contents
46.1. Logical Decoding Examples
46.2. Logical Decoding Concepts
46.2.1. Logical Decoding
46.2.2. Replication Slots
46.2.3. Output Plugins
46.2.4. Exported Snapshots
46.3. Streaming Replication Protocol Interface
46.4. Logical Decoding SQL Interface
46.5. System Catalogs Related to Logical Decoding
46.6. Logical Decoding Output Plugins
46.6.1. Initialization Function
46.6.2. Capabilities
46.6.3. Output Modes
46.6.4. Output Plugin Callbacks
46.6.5. Functions for Producing Output
46.7. Logical Decoding Output Writers
46.8. Synchronous Replication Support for Logical Decoding

PostgreSQL provides infrastructure to stream the modifications performed via SQL to external consumers. This functionality can be used for a variety of purposes, including replication solutions and auditing.

Changes are sent out in streams identified by logical replication slots. Each stream outputs each change exactly once.

The format in which those changes are streamed is determined by the output plugin used. An example plugin is provided in the PostgreSQL distribution. Additional plugins can be written to extend the choice of available formats without modifying any core code. Every output plugin has access to each individual new row produced by INSERT and the new row version created by UPDATE. Availability of old row versions for UPDATE and DELETE depends on the configured replica identity (see REPLICA IDENTITY).

Changes can be consumed either using the streaming replication protocol (see Section 51.3 and Section 46.3), or by calling functions via SQL (see Section 46.4). It is also possible to write additional methods of consuming the output of a replication slot without modifying core code (see Section 46.7).